Tuesday, December 31, 2013

There's been some buzz recently about Kenny Strawn's discovery of Chrome OS Canary (nice work Kenny!). If you're not aware, Canary is a version of Chrome OS that is even more up to date with code changes and new features than dev channel. So it goes stable --> beta --> dev --> canary with stable being the most stable, reliable and least often updated version and canary being the least stable and least reliable but most often updated. A Canary version of the Chrome browser has been available and can be run in parallel with other Chrome channels on Windows and Mac for some time but there's been no publicly known equivalent for Chrome OS until Kenny's discovery and normally, your Chromebook is only on one channel of Chrome OS, switching between channels meant a USB recovery or powerwash.

So Canary is going to give you the latest and greatest Chrome OS features weeks or months before stable channel gets them but you sacrifice the stability of your Chromebook because Canary isn't tested nearly as heavily as stable channel is. What if we could run stable channel on our Chromebook and only boot into Canary channel when we wanted to test something or check out a new feature? Wouldn't that be handy? Well, here are instructions:

To get started, make sure your Chromebook is in developer mode. Model-specific instructions can be found here.

Turn your Chromebook off then turn it back on but do not login. Make sure you have a WiFi or Ethernet connection configured at this point. 3G/4G is not recommended. Press CTRL+ALT+=> (=> is the forward arrow where the F2 key would be on a PC). Do not use the normal CTRL+ALT+T method to get a shell. Use the CTRL+ALT+=> method while no one is logged in.

Login as user chronos, no password is needed.

Run the command:

sudo crossystem dev_boot_usb=1

this tells your Chromebook to allow booting from USB / SD Card. Note that not all Chromebooks can boot from all USB or SD Card ports. For example, the Acer C710 can't boot from an SD Card and the Samsung Chromebook can't boot from the blue USB 3.0 port. You'll need to use a port on your device that supports booting. When in doubt, start with one of the black USB ports and go from there.

Stick a USB or SD Card of at least 8gb size in your Chromebook and run the command:

rootdev -s -dyou'll get output like:

/dev/sda

or it might say /dev/mmcblk0. Whichever it is, that is the device for your Chromebooks primary drive.

Now run:

sudo fdisk -l | grep Disk

this will list out all drives your Chromebook sees. Your Chromebook's main drive will be listed and you'll see some devices we don't care about like /dev/mapper/blahblahblah. We're looking for the USB or SD Card you inserted (compare sizes). On an Intel Chromebook with a USB drive it's likely to show as /dev/sdb, with an SD Card it's likely to be /dev/mmcblk0. On a ARM-based Chromebook, a USB drive is likely to be /dev/sda and a SD Card, /dev/mmcblk0. Make sure you've got the right device and remember what it is for the next step.

chromeos-install is a script to copy Chrome OS to another drive. Normally the script is meant to copy from a removable device to a SSD or hard drive but we're going in the reverse direction, thus we need the --skip_src_removable and --skip_dst_removable options to turn off those checks. The --skip_vblock option is needed to prevent an error message that should not matter anyway. The --dst option allows you to specify the destination device you determined in the previous 2 steps. So on my Intel-based Pixel Chromebook and using a USB drive I would run exactly:

this command will output some details about the install process and may spit out errors if there's trouble copying to your drive (USB drives and SD Cards fail after awhile, get a new one if you need it).

When the process completes, your Chromebook will reboot. Now with the USB/SD Card still inserted, if you press CTRL+U on the keyboard at the ugly computer screen you'll boot from your new installation on the external card instead of the internal drive. You'll probably notice it's slower, USB 2.0 is very slow compared to SSDs. On first boot, the Chrome OS installation on the external drive will want to repair itself by wiping out the stateful partition (note that this is the stateful partition on your external drive, not the one on your internal drive which should remain untouched). Eventually, after a reboot, you should see Chrome OS boot to the setup process.

Lets confirm we're booted off of the external device by running:

rootdev -s -d

this time, we should see the USB/SD Card's device listed instead of the internal SSDs so we know we're running off the external device.

Now we've got a separate Chrome OS install that we can boot into at will with CTRL+U instead of CTRL+D but we need to switch it to Canary channel. That's easy enough to do by running:

sudo update_engine_client --channel canary-channelsudo update_engine_client --updatethis will install the latest Canary channel update for us on the external device, again leaving the internal device untouched. Now we're up and running! Canary channel without the risk.